Process of operating cement-kilns.



No. 818,018. PATENTED APR. 17, 1906.

H. L. DOHERTY.

PROCESS OF'OPBRATING CEMENT KILNS.

APPLIGATION FILE D JAN. 4, 1906.

%13 attommn (Y1 MM 8 UNITED s'rafrns PATENT FFICE.

PROCESS OF OPERATING CEMENT KILNE.

Specification of Letters Patent.

Patented April 17, 1906.

Application filed January 4,1906. Serial No. 294,664.

To wZZ whom it may concern Be it known that I, HENRYL. DOHERTY, a citizen of the United States, and a resident of Madison, in the county of Dane and State of Wisconsin, have invented a certain new and useful Process of Operating Cement-Kilns, of which the following is a specification.

This invention relates to a process of burning cement in rotary kilns by means of powdered coal, oil, or gas and relates particularly to an improved method of operation whereby the formation of rings incrusting the kiln is eliminated.

In the present practice, especially with the long type of kiln, which has of late come into extensive use, much trouble has been experienced through stoppage of the kiln and imedance of its action through the choking effect of what are known as rings. These rings appear as agglomerations in the kiln at a short distance from the clinkerin'g zone and between the clinkeringzone and stack,

end of the kiln. Their formation appears to be due to the fritting of the nearly-calcined material just prior to its entrance into the clinkering zone The softening or 'fritting of the material at this oint gives riseito'f'adhe sive masses, which asten themselvesto-"th'e Walls of the kiln and buildup littleby little until the bore of the kiln is almost com;

pletely obstructed and further operationis' impossible. often has been necessary in the past to cool the kiln and to subsequently chisel off these incrustations, an operation'requiring much labor and time for its accomplishment. In the meantime the apparatusis lying idle and loss of output, &c., ensues. I

In the clinkering of cement a peculiar series of reactions go on, which results in the generation of heat and simultaneously in a change in density and hardness, the finished clinker being much denser and enormously harder than the calcined or partially-calcined material. To pro erly prevent rings, the combustion must e so conducted and the material must be so fed that on substantial completion of the calcination the material is suddenly exposed to the clinkering heat, whereupon the silica, alumina, calcium, and magnesium combine almost instantaneously, producing a product which has a very high melting-point, and therefore will not stick to the walls of the kiln at the temperature to which it is ordinarily exposed during clinkering. Inasmuch as it is impossible to :walls. wardly, passes through the clinkering zone,

Under such circumstances itarrive at the conditions above mentioned, it

follows that the formation of rings has become a serious problem in the manufacture of cement.

It is the object of this invention to greatly reduce and even entirely prevent the formation of rings in the manufacture of cement clinker.

My invention consists in the use of completely-burned clinker to overcome the present difficulty. For this purpose I return to the up I er part of the kiln a certain proportion 0 the discharged clinker, ordinarily a quantity varying from five to twenty-five per cent. of the total output, this depending upon the nature of the material, the length of flame, and on conditions of combustion. I introduce this clinker into the upper part of the kiln in company with the raw material and-cause it to travel in admixture with the raw material down through the kiln. Owing to the density and hardness of the finished clinker, it having a gravity of ap.

proximately 3.12, the finished clinker w1ll lie at, the bottom of the stream of cement material and will largely prevent contact of the'lighter calcining material with the kiln- Thus the admixture travels down and discharges as finished clinker from the lower end of the kiln. When conditions arise tending to the formation of rings, the finished clinker which has been introduced at the upper end ofthe kiln acts abrasively on such concretions and rapidly removes them from the kiln-lining Should the calcining material frit to any great extent, such fritting will occur around the clinker itself and not on the walls of the kiln, so that the kiln-walls remain at all times smooth and clean and in. a condition best suited for the maximum output. The rough interior of the kiln, always to be observed in ordinary practice, is by my process almost wholly absent, and as a consequence by my process the cement stream is spread uniformly over the entire lower portion of the kiln and receives a uniform application of heat.

In the accompanying drawings, Figure 1 shows a cement kiln in elevation. Fig. 2 illustrates that portion of the kiln in which rings are wont toform and graphically shows the manner in which the heavier burned clinker abrades. a ring formation and destroys it.

In the drawings, 1 is a cement-kiln having I Io ' amount only from five to twenty-five per the housing 2 at its upper end, on which is situated the stack 3. The lower end of the kiln is closed except for the fuel-inlet and clinkering-outlet in the hood 4.

Sis a fuel-feeding pipe through which a blast of air and powdered coal or gas or other fuel is introduced.

6 is a conveyer adapted to feed raw material into the chute 7, whereby a uniform stream of the raw material is caused to enter the kiln.

8 is the clinker-discharge outlet, opening into the chute 9. The latter branches beneath the kiln, forming the legs or passages 10 and 11, theformer being ordinarily larger than the latter. At the point of bifurcation is placed a damper 12, so constructed as to be capable of shifting a greater or lesser quantity of clinker through each leg. The leg 10 discharges clinker into the conveyer 13,which clinker is carried after suitable coolin to the grinding apparatus. The clinker dlscharging through theleg 11 and representing an cent. of the total amount of clinker discharges into the conveyer 15 and is taken through thereby to the upper end of the kiln, Where it is deposited in the bin 16 and is fed by means of the conveyer 17 into the kiln.

In Fig. 2, A A represent a cross-section of that portion of the kiln similarly designated in Fig.1. At 18 is a ring formation of the nearly-calcined material. 19 represents the clinker introduced at the upper end of the to mix with the raw material in so far as it is "to sink to the bottom of the mass.

possible, it being understood that the reater density of the clinker causes it very ar ely The Triln may be otherwise operated in the usual way,

. and during its operation if the formation of incipient rings is observed the damper 12 may be shifted to introduce a larger amount of clinker into the upper part of the kiln, whereupon in the course of time the ring will be seen to disappear and the walls of the kiln to assume a smooth condition. With certain materials it is desirable to introduce the clinker only when rings are seen to be in the process of formation; but, generally speaking, it is desirable to have at all times some finished clinker present in the material, as the conduct of-the kiln is improved by the presence of the clinker in contact with the calcinin and cintering material. Whether or not t is increase in efficiency is due to a catalytic action of the introduced clinker cansipi not be stated definitely. I content myself .that the kiln is loaded with seemingly inert matter. The density of the clinker is such that the introduction into the kiln makes scarcely any perceptible increase in the volume occupied by the material.

In transporting the hot clinker from the lower to the up er end of the kiln a slight loss of heat occurs; ut it is so small an amount as to be negligible. For instance, ordinarily the clinker discharges from the kiln at a temperature of about 1,000 centigrade, and it is cooled to about 500 centigrade at the time of its introduction into the upper end of the kiln. With a kiln capacity of two hundred barrels per day and with ten per cent. of the total clinker returned to the upper end of the kiln the heat lost in transport will amount to 380 X 0.2 X 500 X 200 X 0.1+ 2.2 345,400

' kilogram kalories per day, or with coal having a thermal value of seven thousand kalories this would be equivalent to approximately fifty kilo rams or, one hundred and ten pounds, of 0025 per day, a quantity of fuel which is negligible and which, in fact, is more than compensated for by the ease of operation and general economies resulting from my process.

Having described my invention, I now claim and desire to secure by Letters Patent 1. The process of operating continuous cement-kilns which. consists in admixing with the stream of pulverulent material passing therethrough a modicum of preformed clinker.

2. The process of operating rotary cementkilns which consists in admixing with the stream of pulverulent material passing therethrough a modicum of preformed clinker.

3. The process of operating rotary cementkilns which consists in admixing with the stream of pulverulent material passing there through a modicumof hot preformed clinker.

4. The process of operating continuous cement-kilns which consists in diverting a portion of the stream of finished material flowing therefrom and returning it to and admixing with the inflowing stream of raw cementmaking materials.

5. The process of operating rotary cementkilns which consists in divertin a portion of the stream of finished material owing there from, and returning it to and admixing with the inflowing stream of raw cement-making materials.

6. The process of operating continuous cement-kiln s which consists in abstracting five to twenty-five per cent. of the finished material delivered and returning it to and admixing with the inflowing stream of raw cementmaking materials,

7. The process of operating rotary cement- York and State of New York, this 5th day of kilns WllCh consists i? gbztraritinig five tcii December, A. D. 1905. twentyve per cent. 0 t e nis e materia delivered, and returning it to and admixing HENRY DOHERTY' 5 with the inflowing stream of raw cement- Witnesses:

making materials. 7 FLETCHER P. SCOFIELD,

Signed at New York, in the county of New J. CHAS. ANDREWS. 

